It is quite well known to have a process vacuum system with the gas stream being generated by a vacuum pump which is sensitive to liquid contaminants. Therefore, a liquid separator or filter is positioned between the process vacuum system and the downstream vacuum pump The liquid that is separated from the gas stream by the separator or filter is then collected by a liquid accumulator, and such collected liquid must be periodically purged from the accumulator. Such purging often has been conducted by manually closing a valve between the separator and the accumulator so as to disconnect the accumulator from the separator, while at the same time connecting the accumulator to atmosphere. Unfortunately, this manual process requires operator attention as to the amount of liquid collected in the accumulator. Furthermore, since this is inherently a gravity draining system, the draining process is slow. This is especially critical where the liquid separation at the filter is excessive relative to the time taken for atmospheric purging of the accumulator.